Aircraft may traverse through areas of lightning activity. At times, lightning may strike the aircraft, and more particularly the aircraft propulsion engine(s), causing lightning current to traverse the path of least resistance to the rear of the aircraft. Such a path may be, for example, down the propulsion engine shaft. In such instances, the lightning current will likely travel over a bearing, or series of bearings, dependent on the design of the engine. This means the lightning current path is from the bearing inner race, to a point location on a ball bearing, to a point location on the bearing outer race. The small cross-sectional area of these point locations can result in arcing, and potential micro-damage to the ball bearing. Indeed, when a propulsion engine is rebuilt after a lightning strike, pitting in the bearing(s) is typically observed during the rebuild. Moreover, lightning strikes can also disrupt the digital electronic control system of the engine.
Hence, there is a need for a means of protecting gas turbine propulsion engines from lightning strikes that will either bypass the engine bearings or divide the lightning current over multiple bearings, and that will bypass the digital electronic control system of the engine. The present invention addresses one or more of these needs.